| 1. |
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The Seventeenth Data Release of the Sloan Digital Sky Surveys : Complete Release of MaNGA, MaStar, and APOGEE-2 Data
- 2022
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In: Astrophysical Journal Supplement Series. - : Institute of Physics (IOP). - 0067-0049 .- 1538-4365. ; 259:2
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Journal article (peer-reviewed)abstract
- This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys.
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| 2. |
- Clifton, Luke A, et al.
(author)
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Design and use of model membranes to study biomolecular interactions using complementary surface-sensitive techniques.
- 2020
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In: Advances in Colloid and Interface Science. - : Elsevier. - 0001-8686 .- 1873-3727. ; 277
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Journal article (peer-reviewed)abstract
- Cellular membranes are complex structures and simplified analogues in the form of model membranes or biomembranes are used as platforms to understand fundamental properties of the membrane itself as well as interactions with various biomolecules such as drugs, peptides and proteins. Model membranes at the air-liquid and solid-liquid interfaces can be studied using a range of complementary surface-sensitive techniques to give a detailed picture of both the structure and physicochemical properties of the membrane and its resulting interactions. In this review, we will present the main planar model membranes used in the field to date with a focus on monolayers at the air-liquid interface, supported lipid bilayers at the solid-liquid interface and advanced membrane models such as tethered and floating membranes. We will then briefly present the principles as well as the main type of information on molecular interactions at model membranes accessible using a Langmuir trough, quartz crystal microbalance with dissipation monitoring, ellipsometry, atomic force microscopy, Brewster angle microscopy, Infrared spectroscopy, and neutron and X-ray reflectometry. A consistent example for following biomolecular interactions at model membranes is used across many of the techniques in terms of the well-studied antimicrobial peptide Melittin. The overall objective is to establish an understanding of the information accessible from each technique, their respective advantages and limitations, and their complementarity.
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| 3. |
- Moulin, Martine, et al.
(author)
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Perdeuteration of cholesterol for neutron scattering applications using recombinant Pichia pastoris
- 2018
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In: Chemistry and Physics of Lipids. - : Elsevier. - 0009-3084 .- 1873-2941. ; 212, s. 80-87
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Journal article (peer-reviewed)abstract
- Deuteration of biomolecules has a major impact on both quality and scope of neutron scattering experiments. Cholesterol is a major component of mammalian cells, where it plays a critical role in membrane permeability, rigidity and dynamics, and contributes to specific membrane structures such as lipid rafts. Cholesterol is the main cargo in low and high-density lipoprotein complexes (i.e. LDL, HDL) and is directly implicated in several pathogenic conditions such as coronary artery disease which leads to 17 million deaths annually. Neutron scattering studies on membranes or lipid-protein complexes exploiting contrast variation have been limited by the lack of availability of fully deuterated biomolecules and especially perdeuterated cholesterol. The availability of perdeuterated cholesterol provides a unique way of probing the structural and dynamical properties of the lipoprotein complexes that underly many of these disease conditions. Here we describe a procedure for in vivo production of perdeuterated recombinant cholesterol in lipid-engineered Pichia pastoris using flask and fed batch fermenter cultures in deuterated minimal medium. Perdeuteration of the purified cholesterol was verified by mass spectrometry and its use in a neutron scattering study was demonstrated by neutron reflectometry measurements using the FIGARO instrument at the ILL.
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| 4. |
- Tummino, Andrea, et al.
(author)
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Effects of Aggregate Charge and Subphase Ionic Strength on the Properties of Spread Polyelectrolyte/Surfactant Films at the Air/Water Interface under Static and Dynamic Conditions
- 2018
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 34:6, s. 2312-2323
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Journal article (peer-reviewed)abstract
- We demonstrate the ability to tune the formation of extended structures in films of poly(sodium styrenesulfonate)/dodecyltrimethylammonium bromide at the air/water interface through control over the charge/structure of aggregates as well as the ionic strength of the subphase. Our methodology to prepare loaded polyelectrolyte/surfactant films from self-assembled liquid crystalline aggregates exploits their fast dissociation and Marangoni spreading of material upon contact with an aqueous subphase. This process is proposed as a potential new route to prepare cheap biocompatible films for transfer applications. We show that films spread on water from Marangoni swollen aggregates of low/negative charge have 1:1 charge Spreading binding and can be compressed only to a monolayer, beyond which material is lost to the bulk. For films spread on water from compact aggregates of positive charge, however, extended structures of the two components are created upon spreading or upon compression of the film beyond a monolayer. The application of ellipsometry, Brewster angle microscopy, and neutron reflectometry as well as measurements of surface pressure isotherms allow us to reason that formation of extended structures is activated by aggregates embedded in the film. The situation upon spreading on 0.1 M NaCl is different as there is a high concentration of small ions that stabilize loops of the polyelectrolyte upon film compression, yet extended structures of both components are only transient. Analogy of the controlled formation of extended structures in fluid monolayers is made to reservoir dynamics in lung surfactant. The work opens up the possibility to control such film dynamics in related systems through the rational design of particles in the future.
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| 5. |
- Cárdenas, Marité, et al.
(author)
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Review of structural design guiding the development of lipid nanoparticles for nucleic acid delivery
- 2023
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In: Current Opinion in Colloid and Interface Science. - : Elsevier. - 1359-0294 .- 1879-0399. ; 66
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Research review (peer-reviewed)abstract
- Lipid nanoparticles (LNPs) are the most versatile and successful gene delivery systems, notably highlighted by their use in vaccines against COVID-19. LNPs have a well-defined core–shell structure, each region with its own distinctive compositions, suited for a wide range of in vivo delivery applications. Here, we discuss how a detailed knowledge of LNP structure can guide LNP formulation to improve the efficiency of delivery of their nucleic acid payload. Perspectives are detailed on how LNP structural design can guide more efficient nucleic acid transfection. Views on key physical characterization techniques needed for such developments are outlined including opinions on biophysical approaches both correlating structure with functionality in biological fluids and improving their ability to escape the endosome and deliver they payload.
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| 6. |
- Chang, Debby P., et al.
(author)
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Interfacial properties of POPC/GDO liquid crystalline nanoparticles deposited on anionic and cationic silica surfaces
- 2016
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 18:38, s. 26630-26642
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Journal article (peer-reviewed)abstract
- Reversed lipid liquid crystalline nanoparticles (LCNPs) of the cubic micellar (I-2) phase have high potential in drug delivery applications due to their ability to encapsulate both hydrophobic and hydrophilic drug molecules. Their interactions with various interfaces, and the consequences for the particle structure and integrity, are essential considerations in their effectiveness as drug delivery vehicles. Here, we have studied LCNPs formed of equal fractions of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and glycerol dioleate in the presence of different fractions of the stabilizer Polysorbate 80. We have used a combination of ellipsometry, quartz crystal microbalance with dissipation monitoring and neutron reflectometry to reveal the structure and composition of the adsorbed layer on both anionic silica and cationic (aminopropyltriethoxysilane) silanized surfaces. For both types of surfaces, there is a spread near-surface layer comprising lipid and polymer as well as a sparse coverage of intact particles. The composition of the near-surface layer is very close to that of the particles, in contrast to the lipid bilayer observed with related systems. The interaction is stronger for cationic than anionic surfaces, which is rationalized in terms of the negative zeta potential of the LCNPs. The work shows that the attachment of and spreading from LCNPs is influenced by the properties of the surface, the internal structure, composition and stability of the particles as well as the nature of the stabilizer.
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| 7. |
- Hedegaard, Sofie Fogh, et al.
(author)
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Fluorophore labeling of a cell-penetrating peptide significantly alters the mode and degree of biomembrane interaction
- 2018
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In: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8:1
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Journal article (peer-reviewed)abstract
- The demand for highly efficient macromolecular drugs, used in the treatment of many severe diseases, is continuously increasing. However, the hydrophilic character and large molecular size of these drugs significantly limit their ability to permeate across cellular membranes and thus impede the drugs in reaching their target sites in the body. Cell-penetrating peptides (CPP) have gained attention as promising drug excipients, since they can facilitate drug permeation across cell membranes constituting a major biological barrier. Fluorophores are frequently covalently conjugated to CPPs to improve detection, however, the ensuing change in physico-chemical properties of the CPPs may alter their biological properties. With complementary biophysical techniques, we show that the mode of biomembrane interaction may change considerably upon labeling of the CPP penetratin (PEN) with a fluorophore. Fluorophore-PEN conjugates display altered modes of membrane interaction with increased insertion into the core of model cell membranes thereby exerting membrane-thinning effects. This is in contrast to PEN, which localizes along the head groups of the lipid bilayer, without affecting the thickness of the lipid tails. Particularly high membrane disturbance is observed for the two most hydrophobic PEN conjugates; rhodamine B or 1-pyrene butyric acid, as compared to the four other tested fluorophore-PEN conjugates.
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| 8. |
- Sebastiani, Federica, et al.
(author)
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Night-time oxidation at the air-water interface : co-surfactant effects in binary mixtures
- 2022
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In: Environmental Science. - : Royal Society of Chemistry. - 2634-3606. ; :6, s. 1324-1337
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Journal article (peer-reviewed)abstract
- The ageing of organic-coated aqueous aerosols at night is investigated by reacting NO3 with binary surfactant mixtures floating on water. The surfactants are oleic acid (OA), methyl oleate (MO) and stearic acid (SA). Deuterated surfactants mixed with hydrogenous surfactants were studied using neutron reflectometry to determine the reaction kinetics of organic two-component monolayers with NO3 at the air-water interface for the first time. We measured the rate coefficients for OA monolayers, mixed with hydrogenous co-surfactant MO or SA to be (3 +/- 1) x 10-8 cm2 per molecule per s or (3.6 +/- 0.9) x 10-8 cm2 per molecule per s and MO monolayers mixed with hydrogenous co-surfactant OA or SA to be (0.7 +/- 0.4) x 10-8 cm2 per molecule per s or (3 +/- 1) x 10-8 cm2 per molecule per s. The initial desorption lifetimes of NO3, taud,NO3,1, were 8 +/- 3 ns, 14 +/- 4 ns, 12 +/- 3 ns and 21 +/- 10 ns. The approximately doubled desorption lifetime for MO-SA compared to the other mixtures is consistent with a more accessible double bond associated with the larger area per molecule of MO in the presence of SA facilitating NO3 attack. The significantly slower reactive loss of MO-OA compared to a MO monolayer demonstrates that multi-component surfactant mixtures need to be studied in addition to single-component monolayers. Such a retarded decay would cause the residence time to change from ca. 4 to 22 minutes associated with increased transport distances of surfactant species together with any other pollutants that may be protected underneath the surfactant film.
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| 9. |
- Sebastiani, Federica, et al.
(author)
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Nighttime oxidation of surfactants at the air-water interface : effects of chain length, head group and saturation
- 2018
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In: Atmospheric Chemistry And Physics. - : European Geosciences Union (EGU). - 1680-7316 .- 1680-7324. ; 18:5, s. 3249-3268
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Journal article (peer-reviewed)abstract
- Reactions of the key atmospheric nighttime oxidant NO3 with organic monolayers at the air-water interface are used as proxies for the ageing of organic-coated aqueous aerosols. The surfactant molecules chosen for this study are oleic acid (OA), palmitoleic acid (POA), methyl oleate ( MO) and stearic acid ( SA) to investigate the effects of chain length, head group and degree of unsaturation on the reaction kinetics and products formed. Fully and partially deuterated surfactants were studied using neutron reflectometry (NR) to determine the reaction kinetics of organic monolayers with NO3 at the air-water interface for the first time. Kinetic modelling allowed us to determine the rate coefficients for the oxidation of OA, POA and MO monolayers to be (2.8 +/- 0.7) x 10(-8), (2.4 +/- 0.5) x 10(-8) and (3.3 +/- 0.6) x 10(-8) cm(2) molecule(-1) s(-1) for fitted initial desorption lifetimes of NO3 at the closely packed organic monolayers, tau(d), NO3, 1, of 8.1 +/- 4.0, 16 +/- 4.0 and 8.1 +/- 3.0 ns, respectively. The approximately doubled desorption lifetime found in the best fit for POA compared to OA and MO is consistent with a more accessible double bond associated with the shorter alkyl chain of POA facilitating initial NO3 attack at the double bond in a closely packed monolayer. The corresponding uptake coefficients for OA, POA and MO were found to be (2.1 +/- 0.5) x 10(-3), (1.7 +/- 0.3) x 10(-3) and (2.1 +/- 0.4) x 10(-3), respectively. For the much slower NO3-initiated oxidation of the saturated surfactant SA we estimated a loss rate of approximately (5 +/- 1) x 10(-12) cm(2) molecule(-1) s(-1), which we consider to be an upper limit for the reactive loss, and estimated an uptake coefficient of ca, (5 +/- 1) x 10(-7). Our investigations demonstrate that NO3 will contribute substantially to the processing of unsaturated surfactants at the air-water interface during nighttime given its reactivity is ca. 2 orders of magnitude higher than that of O-3. Furthermore, the relative contributions of NO3 and O-3 to the oxidative losses vary massively between species that are closely related in structure: NO3 reacts ca. 400 times faster than O-3 with the common model surfactant oleic acid, but only ca. 60 times faster with its methyl ester MO. It is therefore necessary to perform a case-by-case assessment of the relative contributions of the different degradation routes for any specific surfactant. The overall impact of NO3 on the fate of saturated surfactants is slightly less clear given the lack of prior kinetic data for comparison, but NO3 is likely to contribute significantly to the loss of saturated species and dominate their loss during nighttime. The retention of the organic character at the air-water interface differs fundamentally between the different surfactant species: the fatty acids studied (OA and POA) form products with a yield of similar to 20% that are stable at the interface while NO3=initiated oxidation of the methyl ester MO rapidly and effectively removes the organic character (<= 3% surface-active products). The film-forming potential of reaction products in real aerosol is thus likely to depend on the relative proportions of saturated and unsaturated surfactants as well as the head group properties. Atmospheric lifetimes of unsaturated species are much longer than those determined with respect to their reactions at the air-water interface, so they must be protected from oxidative attack, for example, by incorporation into a complex aerosol matrix or in mixed surface films with yet unexplored kinetic behaviour.
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